The Endocrine System and Blood Flashcards
(21 cards)
Location of the Major Endocrine Glands
- Hypothalamus
- Pineal gland
- Pituitary gland
- Parathyroid glands
- Thyroid glands
- Thymus
- Adrenal gland
- Pancreas
- Ovary (female), Testis (male)
Summary of Endocrine Glands and Hormones
1) Hypothalamus:
- Controls pituitary gland
- Hormones: TRH, CRH, GnRH, etc.
2) Pineal Gland:
- Regulates sleep
- Hormone: Melatonin
3) Pituitary Gland:
- Master gland, controls other glands
- Hormones: GH, TSH, ACTH, LH, FSH, ADH, Oxytocin
4) Parathyroid Glands:
- Regulates calcium
- Hormone: PTH
5) Thyroid Gland:
- Controls metabolism
- Hormones: T3, T4, Calcitonin
6) Thymus:
- Supports immune system
- Hormone: Thymosin
7) Adrenal Glands:
- Stress and salt balance
- Hormones: Cortisol, Aldosterone, Adrenaline
8) Pancreas:
- Regulates blood sugar
- Hormones: Insulin, Glucagon
9) Ovary (female):
- Reproduction, menstrual cycle
- Hormones: Estrogen, Progesterone
10) Testis (male):
- Sperm production, male traits
- Hormone: Testosterone
Functions of the Endocrine System
- Metabolism
- Control of food intake and digestion
- Tissue development
- Ion regulation
- Water balance
- Heart rate and blood pressure regulation
- Control of blood glucose and other nutrients
- Control of reproductive functions
- Uterine contractions and milk release
- Immune system regulation
Nervous System vs. Endocrine System
Nervous system:
- Neurons
- Neurotransmitter
- Receptors on postsynaptic cell
- Seconds
- Very brief
Endocrine system:
- Epithelial and others
- Hormone
- Receptors on target cell
- Seconds to hours
- May be brief or may last for few days
Main Hormone Actions
- Growth Hormone stimulates growth in most tissues and regulates metabolism
- Antidiuretic hormone (ADH) promotes water retention by kidneys
- Adrenaline increases blood glucose, the use of glycogen by muscle, heart rate and force of contraction
- Noradrenaline causes constriction of blood vessels
- Glucagon causes breakdown of glycogen and fats for use as an energy source
- Insulin increases uptake of glucose, amino acids and fats
- Cortisol increases fat and protein breakdown and increases glucose synthesis from amino acids
- T3, T4 (thyroid hormones) initiate protein synthesis
- LH and FSH: regulate production of reproductive hormones (testosterone and estrogen and progesterone)
Steroid Hormone Action
- Testosterone, estrogen and cortisol
Nonsteroid Hormone Action
- Glucagon and insulin
Pituitary Gland
Master Gland
Secretion of Pituitary Hormones
Anterior pituitary:
- TSH
- ACTH
- MSH
- Beta endorphins Lipoprotein
- LH
- FSH Prolactin
Posterior Pituitary:
- ADH
Regulation of Thyroid Hormone Release:
Positive and Negative Feedback Pathways
1) Stimulation (Positive Feedback Pathway):
- Hypothalamus releases TRH
- TRH stimulates pituitary to release TSH
- TSH stimulates thyroid to produce T3 & T4
2) Inhibition (Negative Feedback):
- Rising T3 & T4 levels inhibit TRH and TSH release
- This prevents overproduction of thyroid hormones
Regulation of Ca+2 by Parathyroid Hormone
- Low blood Ca²⁺ → Parathyroid glands release PTH
PTH increases Ca²⁺ by:
Stimulating bone resorption (releases Ca²⁺)
Increasing Ca²⁺ reabsorption in kidneys
Enhancing vitamin D activation → boosts Ca²⁺ absorption from intestines
- High blood Ca²⁺ → inhibits PTH release (negative feedback)
Regulation of Cortisol Release: Positive and
Negative Feedback Pathways
1) Positive Regulation:
- Hypothalamus releases CRH
- CRH stimulates pituitary to release ACTH
- ACTH stimulates adrenal cortex to produce cortisol
2) Negative Feedback:
- High cortisol levels inhibit CRH and ACTH release
- Prevents excess cortisol production
Regulation of Blood Glucose by Insulin and
Glucagon
High blood glucose → Pancreas releases insulin:
- Insulin promotes glucose uptake by cells & storage as glycogen
- Result: Blood glucose decreases
Low blood glucose → Pancreas releases glucagon:
- Glucagon stimulates glycogen breakdown in liver
- Result: Blood glucose increases
Responses to Stress
1) Immediate (Short-term) – “Fight or Flight”:
- Adrenal medulla releases adrenaline & noradrenaline
- Increases heart rate, blood pressure, energy availability
2) Long-term Stress:
- Hypothalamus → CRH → ACTH → Adrenal cortex
- Adrenal cortex releases cortisol
- Cortisol increases blood glucose, suppresses immune response, helps maintain energy
Functions of Blood
- Transport of gases, nutrients and waste products; e.g. oxygen
- Transport of processed molecules; e.g., precursor of vitamin D from skin to liver then kidneys
- Transport of regulatory molecules; e.g., hormones
- Regulation of pH and osmosis (normal pH of most body tissues between 7.35 and 7.45)
- Maintenance of body temperature; e.g., warm blood shunted to the interior of the body
- Protection against foreign substances; e.g.,
antibodies - Clot formation
Blood Composition
Plasma (55%):
Mostly water, contains proteins (albumin, globulins, fibrinogen), electrolytes, hormones, nutrients, and waste products.
Red Blood Cells (RBCs, 45%):
Carry oxygen (via hemoglobin) and carbon dioxide.
White Blood Cells (WBCs, <1%):
Immune function; fight infections.
Platelets (<1%):
Blood clotting.
Structure of the Haemoglobin Molecule
- 250 million Hb molecules per RBC - 1 billion O2 molecules per RBC
Altitude Exposure Stimulates RBC Formation
- More red blood cells stimulated from red bone marrow
Red Blood Cell Formation (Haemopoeisis)
Location: Primarily in bone marrow
Process:
1) Stem cells differentiate into erythroblasts.
2) Erythroblasts mature into reticulocytes.
3) Reticulocytes lose their nucleus and become mature red blood cells (RBCs).
Regulation: Stimulated by erythropoietin (EPO) from the kidneys in response to low oxygen levels.
Normal Blood Values
Haemoglobin:
Female (Hb) = 115-165 g/L
Male (Hb) = 130-180 g/L
Haematocrit:
Female Hct - 37-47%
Male Hct = 40-54%
Blood Oxygen Content
Arterial O2 content (ml/dl) = {1.36 x [Hb] x O2 sat} + [0.003 x PaO2)
- 1.36 = amount of O2 in 1 gram of Hb
- Hb - 14-16 g/dL
- Normal value of arterial O2 content in men and women is 17-20ml of O2/dL or 170-200ml/L of blood
